Among the hundreds of new laws taking effect Tuesday (Oct. 1) is one meant to help the Chesapeake Bay by limiting when, where and how Marylanders should feed their lawns. One scientist, though, suggests homeowners could help the bay better by forgoing lawn fertilizer altogether.

The Fertilizer Use Act of 2011 restricts the nutrient content of all grass food sold in Maryland, barring phosphorus from most lawn-care products and setting limits on how much nitrogen should be applied. Though passed two years ago, its onset was delayed until now to give lawn-care companies time to train and certify their employees to meet new requirements.

The law prohibits feeding a lawn from Nov. 15 until March 1, for instance. It also bars spreading near a water way or putting fertilizer down when heavy rain is forecast. And it forbids using fertilizer to de-ice sidewalks and driveways.

Virginia adopted a similar law last year, with regulations to take effect next year, while Pennsylvania has yet to act.

Maryland agriculture officials pushed the measure as a matter of equity, saying homeowners needed to join farmers in cutting back on fertilizer use to help the bay, since turf grass covers almost as much land now as do farm crops.

The law sailed through Annapolis with the support of many environmentalists. It also won the backing of lawn-care companies, who embraced the official argument that "healthy" lawns are needed to curb polluted runoff to the bay -- and the best way to keep turf healthy is to feed it regular, controlled doses of fertilizer.

"Look, lawn fertilizer is for aesthetic reasons only," Fisher said in an interview on the eve of the law taking effect. The Chesapeake Bay is overloaded with fertilizer -- its primary problem is too much fertilizer. Why do we need fertilizer on lawns at all?.

"I've never fertilized a lawn that I've owned," he added. "It’s not as thick and green, as lush as ones you see in ChemLawn ads, but it's green. I only have to cut it every other week."

Fisher says studies show thick lawns do prevent sediment runoff better than scraggly yards, especially on slopes. But he says research also has found that nitrogen runs off fertilized lawns, in some cases at rates on par with runoff from farm fields.

"The devil's in the details on this," he said, "but there are lots of situations where fertilized lawns can lose as much nitrogen and phosphorus as a cornfield. So from the environmental perspective, that's something we can't afford right now."

Fisher contends that in most cases lawns can get all the nutrients they need from nitrogen and phosphorus in the air, and from leaving grass clippings behind after mowing to recycle their nutrients.

The lawn-care industry takes issue with Fisher's stance. Vernon Cooper, immediate past president of the Maryland Turfgrass Council said turf specialists with UM's extension service have concluded that nutrients won't run off well-maintained lawns that are fed within the limits set by the law.

All fertilizers sold in Maryland now must have label directions specifying that no more than 0.9 pounds of nitrogen be applied per 1,000 square feet of lawn, with at least 20 percent of the nutrient to be in slow-release form. By feeding your lawn no more than two pounds of nitrogen a year, Cooper contended, "it won't leach on through."

Cooper described lawn care as a kind of Catch 22, trying to prevent sediment runoff without allowing nutrient runoff.

"You need [to apply] nitrogen to keep the turf actively growing so you don't lose the phosphorus," he said, "but you need to use the smallest amount of nitrogen possible to avoid contaminating the waterways."

Cooper acknowledged that homeowners could reduce how much nitrogen their lawns need by leaving grass clippings after mowing, but he argued that wouldn't be enough to keep the grass thick and green.

Fisher suggested another way to avoid the debate over whether to fertilize a lawn or not, by getting rid of the turf altogether.

"In urban and suburban landscapes, what's the best way to eliminate nutrient runoff? Put as much in trees and shrubbery as you can," he said.